Silicone aqueous emulsion release liquid and release film using the same

ABSTRACT

A release agent and a release liquid which are used for the manufacture of labels, double-sided tapes, etc., are disclosed. The release agent and the release liquid provide improved adhesion between a substrate and a release layer, and excellent peel strength betwveen the release layer and an adherent. The release agent includes a dispersion of a vinyl-modified colloidal silica, a dispersion of a platinum chelate catalyst, and a polysiloxane water-dispersible silicone emulsion. The release liquid is obtained by dispersing the release agent in water so as to have a solid content of 2.5˜30% by weight. The release film is produced by applying the release liquid on a substrate, followed by drying.

RELATED U.S. APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO MICROFICHE APPENDIX

Not applicable.

FIELD OF THE INVFNTION

The present invention relates to a release agent and a release liquidwhich are used for the manufacture of adhesive labels, peel-offlabelstickers, double- sided tapes, etc., and to a release film using therelease liquid. In particular, the present invention relatcs to arelease liquid obtained by dispersing a mixture of an aqueous emulsionsilicone release agent and a modified colloidal silica in water, and arelease film using the release liquid as a release layer. The releasefilm according to the present invention has greatly improved adhesivestrength between a substrate and the release layer and excellent peelstrength between the release layer and an adherent.

BACKGROUND OF THE INVENTION

In general, as shown in FIG. 1, a release film is produced by applying arelease liquid as a release layer 2 on a substrate 1 such as a plasticfilm, a sheet, a paper or a non-woven fabric at a predeterminedthickness. For example, U.S. Pat. Nos. 5,672,428 and 5,728,339 disclosea release layer obtained by forming a plastic film or sheet as asubstrate, followed by applying a release agent thereon.

However, conventional release films usingthe release layerhavedisadvantagesofinadequate peel strength and adhesive strength. That is,a peel strength sufficient to release a release film from an adherentafter the release film is contacted with the adherent results in weakadhesive strength between the substrate and the release agent. Inaddition, the release film causes problems such as peeling off of therelease agent from the substrate and poor solvent resistance.

There have been known a number ofinethods for improving the adhesionbetween a substrate and a release agent. For example, when a plasticfilm is used as the substrate, the surface of the plastic film ischemically treated with chromic acid, ozone, corona, flame, radioactiveion beam, etc. In particular, when the plastic film is a polyester film,the surface of the plastic film is treated with a highly polar polymersuch as modified polyester having a high affinity, a partiallyhydrolyzed ethylene-vinyl acetate copolymer, polyvinylbutyral, etc.

In addition, methods for improving the peel strength between a releaselayer and an adherent, and the adhesion between a substrate and therelease layer have been known. For example, U.S. Pat. No. 5,298,325suggests a method for forming a release layer by forming a primer layeron a substrate, followed by off-line coating on the primer layer.However, the patent has problems in terms of complex processes includingthe off-line coating, and increased manufacturing cost.

In common release films, increasing of the adhesive strength between arelease layer and a substrate results in low peel strength, andincreasing of peel strength to improve the releasability results in lowadhesive strength between the release layer and the substrate.

According to U.S. Pat. Nos. 5,672,428 and 5,728,339, a release film isproduced by in-line coating a plastic substrate once with a siliconeaqueous emulsion release agent. At this time, an adhesion promoter isadded to the release agent to improve adhesion between the film and therelease agent. Examples of the adhesion promoter used herein includewater-dispersible polyester, water-dispersible acrylic resin,glycidoxyalkoxysilane, etc.

On the other hand, a stretching operation must be performed during thein-line coating of the plastic film with the release agent. At thistime, the operation requires considerable care so as not to cause pooradhesion between the release agent and the substrate, and smoothness ofthe release layer. When in-line coating the plastic substrate with therelease agent, poor smoothness of the release layer results fromirregular contraction and expansion of the release layer duringstretching or annealing operation following coating the release agent,or from partial cross-linking caused by different cross-linking ratesdue to non-uniform heat transfer between the release layer and thesubstrate.

BRIEF SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of the aboveproblems, and it is an object of the present invention to provide arelease film having an excellent adhesive strength between a substrateand a release agent, and having excellent peel strength between therelease film and an adherent.

It is another object of the present invention to provide a simplifiedmanufacturing process of the release film by using a silicone aqueousemulsion release agent containing a vinyl-modified colloidal silica,instead of a release agent containing an organic solvent, therebycausing no volatilization of organic solvent during producing therelease film, and forming the release layer by in-line coating.

In accordance with the present invention, there is provided a siliconeaqueous emulsion release agent comprising:

1˜10% by weight of a dispersion of a vinyl-modified colloidal silicahaving a solid content of 10˜40% by weight;

0.1˜5% by weight of a dispersion of aplatinum chelate catalyst having asolid content of 12˜25% by weight; and

the remaining amount of a polysiloxane water-dispersible siliconeemulsion having a solid content of 30˜60% by weight.

In accordance with the present invention, there is provided a siliconeaqueous emulsion release liquid obtained by dispersing the siliconeaqueous emulsion release agent in water so as to have a solid content of2.5˜30% by weight.

In accordance with the present invention, there is provided a releasefilm produced by applying the silicone aqueous emulsion release liquidon a substrate.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanying drawing.

FIG. 1 is a cross-sectional view schematically showing a common releasefilm.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be explained more detail.

The dispersion of a modified colloidal silica used in the presentinvention is obtained by reacting 10˜30% by weight of a colloidal silicawith an alkoxysilane compound or polymer having a vinyl group and, atthe same time, dispersing the reaction mixture in water. Thevinyl-modified colloidal silica used has a polar hydroxyl group capableof increasing binding strength with a substrate at the center of thesilica core, and a vinyl group capable of chemically binding with thepolarhydroxyl group. However, the vinyl-modified colloidal silicamustnot decrease the releasability of a release agent. The vinyl-modifiedcolloidal silica is obtained by the reaction of a colloidal silica andvinylalkoxysilane. At this time, the vinylalkoxysilane undergoeshydrolysis and condensation with a hydroxyl group on the surface of thecolloidal silica to obtain the vinylmodified colloidal silica having avinyl group. In addition, aminotrialkoxysilane having an amino group ishydrolyzed and reacted with carboxylic acid containing an amino groupand a vinyl group on the surface of the silica to obtain thevinyl-modified colloidal silica having a vinyl group. Furthermore, anorganic silane polymer having amine groups is directly reacted with acolloidal silica and further reacted with a carboxyl compound having avinyl group to obtain the vinyl-modified colloidal silica.

The organic silane compound having a vinyl group which can react with acolloidal silica to obtain the vinyl-modified colloidal silica, isselected from the group consisting of vinyltrimethoxysilane,vinyltriethoxysilane, allyltrimethoxy-silane, allyltriethoxysilane,3-(trimethoxysilyl)propyl acrylate, 3-(trimethoxysilyl)propylmethacrylate, 3-(triethoxysilyl)propyl acrylate,3-(triethoxysilyl)propyl methacrylate,N-[3-(trimethoxysilyl)propyl]-N′-(4-vinylbenzyl)ethylenediaminehydrochloride and mixtures thereof.

The organic silane compound having an amine group which can react with acolloidal silica to obtain the vinyl-modified colloidal silica, isselected from the group consisting of γ-aminopropyltrimethoxysilane,γ-aminopropyltriethoxysilane, γ-aminopropylmethyldimethoxysilane,γ-aminopropyldimethylethoxysilane,N-phenyl-γ-aminopropyltrimethoxysilane,N-phenyl-γ-aminopropyltriethoxysilane,N-β-(aminoethyly-γ-aminopropyltrimethoxysilane,N-β-(aminoethyl)-γ-aminopropyltriethoxysilane,N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane,N-β-(aminoethyl)-γ-aminopropyldimethylethoxysilane, N′-[3-(trimethoxysilyl)propyl]diethylenetriamine,N-[4-(trimethoxysilyl)butyl]ethylenediamine and mixtures thereof.

Examples of vinyl monomer having a carboxyl group which can react withthe amine-modified colloidal silica to obtain the vinyl-modifiedcolloidal silica includeacrylic derivatives and methacrylic acidderivatives, etc., and the vinyl monomer is preferably selected from thegroup consisting of acrylic acid, methacrylic acid, itaconic acid,vinylacetic acid, vinylpropionic acid and mixtures thereof.

Examplesofcondensation polymerhavingorganicsilane groupsto obtainthevinyl-modified colloidal silica includeN-[3-(trinmethoxysilyl)propyl]polyethyleneiminehydrochloride,N-[3-(trimethoxysi lyl)propyl] polyethyleneimine, etc.

The particle size of the vinyl-modified colloidal silica used in thepresent invention is preferably within the range of from 1 nm to 500 nm,and more preferably within the range of from 1 nm to 100 nm. Inaddition, the solid content ofthc vinyl-modified colloidal silica ispreferably within the range of 1˜10% by weight, based on the weight ofthe release liquid. When the solid content is less than 1% by weight,binding strength with the substrate is insufficient. When the solidcontent is more than 10% by weight, the degree of cross-linking anddispersibility are poor, and smoothness of the release layer isdeteriorated.

The platinum chelate catalyst used in the present invention has a solidcontent of 12˜25% by weight in a water-dispersible solution, and isincluded in an amount of 0.1˜5% by weight within the release agent.Examples of the platinum chelate catalyst include carbon-supportedplatinum or silica-supported platinum, chloroplatinate, platinum-olefincomplexes, platinum-alcohol complexes, platinum-amine complexes,platinum coordination compounds, etc. Using less than 0.1% by weight ofthe platinum chelate catalyst causes contamination due to slow curingduring the coating step, while using more than 5% by weight does notsignificantly increase the curing rate, and is thus economicallydisadvantageous.

The polysiloxane water-dispersible emulsion release agent comprises30˜40% by weight of a vinylpolysiloxane resin, 1˜10% by weight of ahydropolysiloxane resin, 0.1˜5% by weight of a non-ionic surfactant andthe remaining amount of water. The solid content of the polysiloxanewatcr-dispersible emulsion release agent is preferably within the rangeof 30˜60% by weight. The average particlesize of the polysiloxanewater-dispersible emulsion release agent is preferably within the rangeof 0.01˜1 μm.

Vinyl groups included in the vinylpolysiloxane resin may be bonded toany positions within the resin molecule, and preferably may be bonded tothe end portions of the molecule. In addition, the molecule may be alinear or branched structure, ora combination thereof. Instead ofinethylgroup, hydrocarbons having 1 to 20 carbon atoms which are unsubstitutedor substituted may be bound to the silicon atom. Examples of thesehydrocarbons include alkyl groups such as ethyl group, propyl group,butyl group, hexyl group, dodecyl group, tetradecyl group, hexadecylgroup, octadecyl group, etc.; aryl groups such as phenyl group, tolylgroup, etc.; and -phenylethyl group, -phenylhydrocarbon group,chloromethyl group, 3,3,3-trifluoropropyl group, etc. However, thecontent of methyl group must be not less than 70 mol % and morepreferably not less than 80 mol % in terms of better smoothness andreleasability. When the content of methyl group is less than 70 mol %,smoothness and releasability are poor. The viscosity of thevinylpolysiloxane is, but is not particularly limited to, within therange of from 10 to 10,000 cSt at 25° C., and preferably within therange of form 1000 to 5,000 cSt. When the viscosity is less than 10cSt,curing is difficult. When the viscosity is more than 10,000 cSt, surfacesmoothness is poor.

The hydropolysiloxane resin used as a curing agent in the presentinvention may be a linear, branched, cyclic structure, or a combinationthereof, but is limited to these structures. The viscosity and molecularweight of the hydropolysiloxane resin are not limited, so long as thehydropolysiloxane resinlhas agood compatibility withthevinylpolysiloxane resin. The amount of the hydropolysiloxane resinused is determined so that the number of hydrogen atoms bound to onesilicon atom per one vinyl group of the vinylpolysiloxane resin ispreferably within the range of 0.5˜1. When the number of hydrogen atomsbound to one silicon atom per one vinyl group is less than 0.5, it isdifficult to obtain a good curability. When the number of hydrogen atomsbound to one silicon atom per one vinyl group is more than 5, elasticityand physical properties after curing are poor.

When hydropolysiloxane is used in an amount exceeding the amount ofvinylpolysiloxane, crosslinking is progressed to decrease theflexibility, thereby causing cracks on the membrane and thus decreasingsmoothness.

Examples of the non-ionic surfactant used in the present inventioninclude polyoxyethylene alkylether, polyoxypropylene alkylether,polyoxyethylene alkylphenylether, polyethyleneglycol fatty acid esters,sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters,glycerin fatty acid esters, polyoxyethyleneglycerin fatty acid esters,polyglycerin fatty acid esters, propyleneglycol fatty acid esters, andmixtures thereof. Polyoxyethylene alkylether and polyoxyethylenealkylphenylether are preferable.

The average particle diameter of the colloidal silica and sphericalsilicone resin contained in the silicone aqueous emulsion release agentand the release liquid are preferably within the range of 0.001˜100 μm.It is very difficult to obtain the colloidal silica and sphericalsilicone resin having an average particle diameter smaller than 0.001μm. When the average particle diameter is larger than 100 μm, stabilityof emulsion and surface smoothness are unsatisfactory.

The silicone aqueous emulsion release liquid according to thepresentinvention can beapplied on plastic films such as polyester,polypropylene, polyethylene, polyvinylchloride, nylon, etc., kraftpapers, non-woven fabrics, clothes, etc. The release liquid according tothe present invention preferably has a solid content of 2.5˜20% byweight.

After the substrate is surface-treated by corona, to strengthen thechemical bonding between the release layer, its surface is appliedagent. The thickness of the substrate is the range of. 20˜1500 μm. Inaddition, in order to fully strengthen the chemical bonding between therelease layer, a chemically treated layer such as a primer layer can bepreviously formed between the substrate and the release layer. Fhethickness of the release layer is preferably thinner than 5 μm, and morepreferably thinner than 3 μm.

Hereinafter, the present invention will be described in more detail withreference to the following Examples. However, these examples are givenfor the purpose of illustration and not of limitation.

[Preparative Example 1]

10 parts by weight of allyltrimethoxysilane was added dropwise to 100parts by weight of a colloidal silica (silica solid content: 30% byweight, average particle size: 7 nm) with vigorous stirring at roomtemperature over 1 hour, and then the mixture was maintained for 2hours. Thereafter, the mixture was raised to 80° C., and further reactedfor 6 hours to obtain a vinyl-modified colloidal silica.

[Preparative Example 2]

100 parts by weight of a colloidal silica (silica solid content: 30% byweight, average particle size: 7 nm) was charged into a three-neck flaskequipped with a nitrogen inlet, a stirrer and a thermometer undernitrogen atmosphere, and then 5 parts by weight of-aminopropyltrimethoxysilane was added dropwise thereto with vigorousstirring, and the mixture was maintained for 2 hours. Thereafter, themixture was raised to 80° C., and then maintained for 6 hours to obtainan amine-modified colloidal silica. The reaction mixture was allowed tocool to room temperature, and 5 parts by weight of vinyl acetic acid wasadded thereto with vigorous stirring to obtain a vinyl-modifiedcolloidal silica.

[Preparative Example 3]

100 parts by weight of a colloidal silica (silica solid content: 30% byweight, average particle size: 7 nm) was charged into a three-neck flaskequipped with a nitrogen inlet, a stirrer and a thermometer undernitrogen atmosphere, and then 50 parts by weight ofN-[3-(trimethoxysilyl)propyl]polyethyleneimine hydrochloride (30%aqueous solution) was addedthereto with vigorous stirring at roomtemperature. Thereafter, the reaction mixture was raised to 60° C., andfurther reacted for 8 hours. The reaction mixture was allowed to cool toroom temperature, and 5 parts by weight of acrylic acid was addedthereto to obtain a vinyl-modified colloidal silica.

[Example 1]

350g of methylvinylpolysiloxane (vinyl-terminated polysiloxane,molecular weight: 780) and 70g of methylhydrogen polysiloxane (130 cSt)were charged into a reactor and mixed at 2,000 rpm using a homomixer. Tothe mixture was added 5 g of polyoxyethylenelauryl ether (9 mole), 5 gof polyoxyethylenelauryl ether (23 mole) and 100 g of water. Thereafter,the reaction mixture was stirred at 6,000 rpm. When viscosity started toincrease, stirring rate was reduced to 2,000 rpm. 270g of water wasadded to the reaction mixture. The mixture was mixed using ahigh-pressure homomixer, and then diluted with 200g of distilled waterto obtain an aqueous emulsion.

100 parts by weight of the aqueous emulsion was transferred into areactor equipped with a stirring apparatus, and then diluted with 300parts by weight of distilled water. 5 parts by weight of awater-dispersible solution containingchloroplatinate-olefin complex(solid content 20% by weight) and 10 parts by weight of the modifiedcolloidal silica obtained in Preparative Example 1 were added to thedilution while stirring at room temperature. The mixture was stirred for12 hours to obtain a homogeneous white silicone water-dispersibleemulsion release liquid. The release liquid thus obtained was dried at atemperature of 105° C. for 3 hours. The content of non-volatilecomponents in the release liquid was shown to be 12% by weight, and theaverage diameter of the particles in the release liquid was measured tobe 0.1 μm using an electron microscope.

A biaxially stretched polyester film to be applied with the siliconeresin was prepared in accordance with a conventional process. That is,after an unstretched film was extruded at 250° C.˜300° C., the extrudedfilm was stretched to 5 times in both transverse and longitudinaldirections, respectively, at a temperature of 100° C. While thestretched film was passed through a coater, one or both sides of thefilm were applied with a release agent. The applied film was heat-setunder wind speed of 20 m/s at a temperature of 200° C. for 20 seconds toproduce a release film.

[Example 2]

A release film was produced in the same manner as in Example 1, exceptthat 380 g of methylvinylpolysiloxane (vinyl-terminated polysiloxane,molecular weight: 780) and 40 g of methylhydrogenpolysiloxane(viscosity: 130cSt) were used.

[Example 3]

A release film was produced in the same manner as in Example 1, exceptthat 400g of methylvinylpolysiloxane (vinyl-terminated polysiloxane,molecular weight: 780) and 20g ofmethylhydrogenpolysiloxane(viscosity:130 cSt) were used. The releasefilmthusproduced was dried at room temperature to obtain as an elastic whitepowder. The powder was confirmed by an electron microscope that it has aparticle size of 1 μm as spherical particles.

[Example 4]

A release film was produced in the same manner as in Example 2, exceptthat 575 parts by weight of distilled water was used.

[Example 5]

A release film was produced in the same manner as in Example 2, exceptthat 200 parts by weight of distilled water was used.

[Example 6]

A release film was produced in the same manner as in Example 2, exceptthat the vinyl-modified colloidal silica obtained in Preparative Example2 was used.

[Example 7]

A release film was produced in the same manner as in Example 2, exceptthat the vinyl-modified colloidal silica obtained in Preparative Example3 was used.

[Example 8]

A release film was produced in the same manner as in Example 2, exceptthat 10 parts by weight of the vinyl-modified colloidal silica obtainedin Preparative Example 2 was used.

[Example 9]

A release film was produced in the same manner as in Example 2, exceptthat 40 parts by weight of the vinyl-modified colloidal silica obtainedin Preparative Example 1 was used.

[Comparative Example 1]

A release film was produced in the same manner as in Example 2, exceptthat the vinyl-modified colloidal silica was not used.

[Comparative Example 2]

A release film was produced in the same manner as in Example 2, exceptthat the vinyl-unmodified colloidal silica (silica solid content: 30% byweight, average particle size: 7 nm) was used.

[Comparative Example 3]

A release film was produced in the same manner as in Example 1, exceptthat the modified colloidal silica was not used.

[Comparative Example 4]

A release film was produced in the same manner as in Example 3, exceptthat the modified colloidal silica was not used.

Physical properties of the release films produced in Examples andComparative Examples were measured. The results were shown in Table 1below. The measurement of the physical properties was carried out inaccordance with the following methods. The measurement of peel strength,percentage of residual adhesive and adhesive strength was carried outusing Surface Property Tester (HEIDON 14DR). The conditions for themeasurement were as follows:

peeling angle: −180°

peeling rate: 300 mm/min

sample size: 4 cm×15 cm

sample size for measuring peel strength (g/in): 100 mm

The measurement was repeated five times, and the measured values wereaveraged.

1. Peel strength

Preparation of sample

1. A sample coated with silicone was maintained at 23° C. and 65% RH for24 hours.

2. After a standard adhesive tape (TESA7475) was adhered to the surfaceof the silicone-coated sample, the sample was pressed under a load of20g/cm² at 60° C. for 20 hours.

3. After the pressed sample was maintained at 23° C. and 65% RH for 3hours, the physical properties of the sample were measured.

Instrument: Surface Property Tester (HELDON 14DR)

Method:

1. Peeling angle: 180°, Peeling rate: 300 mm/min.

2. Sample size: 400 mm×1500 mm, Sample size for measuring peel strength:100 mm

Data: The unit of peel strength is g/in. The measurement was repeatedfive times, and the measured values were averaged.

2. Percentage of residual adhesive

Preparation of sample

1. A sample coated with silicone was maintained at 23° C. and 65% RH for24 hours.

2. After a standard adhesive tape (TESA7475) was adhered surface of thesilicone-coated sample, the sample was pressed under a load of 20g/cm²at 60° C. for 20 hours.

3. After the pressed sample was maintained at 23° C. and 65% RH for 3hours, the peel strength of the sample was measured.

4. The adhesive tape was removed and kept so as to leave no contaminantson the adhesive tape, and a cleanPET film was placed on the surf ace ofthe tape was pressed by one reciprocation using a tape roller having aweight of 2 kg (ASTM D- 1000-55T).

5. Measurement of peel strength

Instrument: Surface Property Tester (HEIDOIN 14DR)

Method:

1. Peeling angle: 180°, Peeling rate: 300 mm/min.

2. Sample size: 400 mm×1500 mm, Sample size for measuring peel strength:100 mm

3. Data${{Percentage}\quad {of}\quad {residual}\quad {adhesive}} = {\frac{\begin{matrix}{{peel}{\quad \quad}{strength}\quad {of}\quad {adhesive}\quad {tape}\quad {after}} \\{{{measur}{ing}}\quad {release}\quad {peel}\quad {strength}}\end{matrix}}{{peel}\quad {strength}\quad {of}\quad {new}\quad {adhesive}\quad {t{ape}}\quad {on}\quad {PET}\quad {film}} \times 100}$

3. Change in adhesive strength of sample

Preparation of sample:

1. A polyester film coated with silicone was aged in a Convection Oven(Heraeus, Model HC 4033) at 60° C. and 70% RH for 7 days.

2. After the aged film was maintained at 23° C. and 65% RH for 3 hours,a standard adhesive tape (TESA7475) was adhered to the surface of thesilicone-coated sample to measure the peel strength of the sample.

Instrument: Surface Property Tester (HEIDON 14DR)

Method:

1. Peeling angle: 180°, Peeling rate: 300 mm/min.

2. Sample size:4 cm×15 cm, Sample size for measuring peel strength: 100

Data${{Change}\quad {in}\quad {peel}\quad {{strength}{\quad \quad}(\%)}} = {\frac{\begin{matrix}{{{peel}\quad {strength}\quad {{bef}{ore}}\quad {aging}} -} \\{{p{eel}}\quad {strength}\quad {after}\quad {aging}}\end{matrix}}{{peel}\quad {strength}\quad {before}\quad {aging}} \times 100}$

4. Solvent resistance

Preparation of sample:

1. A sample coated with silicone was maintained at room temperature (30°C.) for 3 hours.

2. The surface of the silicone-coated sample was reciprocately rubbed 10times using cotton swabs containing methylethyl ketone and acetone,respectively, at constant pressure, and then physical properties of thesample were measured.

Method: The physical properties were identified using an electronmicroscope (Hitachi, Model S2000-150) under 300 power magnification.

Data: The physical properties of the sample were evaluated based on thefollowing criteria.

1. ⊚(excellent): No erasing or peeling was observed.

2. ∘(good): Slight erasing and peeling were observed.

3. Δ(average): Some erasing and peeling were observed.

4. x (poor): Distinct erasing and peeling were observed.,

As described in above Examples and Comparative Examples, since therelease film according to the present invention uses the siliconeaqueous emulsion release agent containing the vinyl-modified colloidalsilica, no organic solvent is volatilized during producing the releasefilm, and the release film is easily produced by in-line coating. Therelease film according to the present invention has greatly improvedadhesive strength between a substrate and a release layer, and excellentpeel strength between the release layer and an adherent.

Therefore, the release film according to the present invention can beused in various products such as adhesive labels, peel-off labelstickers, double-sided tapes, etc.

TABLE 1 Change in Percentage adhesion of with residual substrate Releaseliquid composition Peel Strength adhesive after Solvent (A) (B) (C) (D)(E) (F) (G) (Average ± S.D.) (%) aging (%) Resistance Exa. 1 35 7 3.18 01 3 375 5.2 ± 0.4 6.1 ± 0.7 89 11.0 ⊚ Exa. 2 38 4 3.18 0 1 3 375 5.3 ±0.2 6.4 ± 0.4 95.3 9.5 ⊚ Exa. 3 40 2 3.18 0 1 3 375 7.1 ± 0.3 7.5 ± 0.588.2 18 ◯ Exa. 4 38 4 3.18 0 1 3 375 5.4 ± 0.3 6.4 ± 0.4 93.8 22 ⊚ Exa.5 38 4 3.18 0 1 3 275 6.1 ± 0.3 7.7 ± 0.5 92.4 33 ⊚ Exa. 6 38 4 4.0 0 13 373 5.3 ± 0.4 6.4 ± 0.5 94.7 23 ⊚ Exa. 7 38 4 2.91 0 1 3 375 6.5 ± 0.38.1 ± 0.5 93.2 35 ⊚ Exa. 8 38 4 1.59 0 1 3 368 7.3 ± 0.4 8.7 ± 0.7 88.025 ◯ Exa. 9 38 4 6.36 0 1 3 388 8.9 ± 0.5 9.7 ± 0.8 90.3 15 ⊚ Comp. .8 40 0 1 1 361 7.1 ± 1.2 13.4 ± 1.9  83.5 92 Δ Exa. 1 Comp. 38 4 0 2.5 1 3376 7.9 ± 1.7 18.7 ± 2.4  85.0 140 X Exa. 2 Comp. 35 7 0 0 1 1 361 6.1 ±1.4 17.5 ± 5.7  82.3 220 Δ Exa. 3 Comp. 40 2 0 0 1 1 361 7.1 ± 1.9 23.4± 6.3 81.3 270.5 Δ Exa. 4 (A): Vinylpolysiloxane (B): Hydropolysiloxane(C): Vinyl-modified colloidal silica (D): Unmodified colloidal silica(E): Platinum chelate catalyst (F): Surfactant (G): Water

We claim:
 1. A method of preparing a silicone aqueous emulsion releaseliquid comprising: preparing a silicone aqueous emulsion release agenthaving 1-10% by weight of a dispersion of a vinyl-modified colloidalsilica with a solids content of 10-40% by weight, 0.1-5% by weight of adispersion of a platinum chelate catalyst with a solids content of12-25% by weight, and a remaining amount of the silicone aqueousemulsion release agent being of a polysiloxane water-dispersiblesilicone emulsion with a solids content of 30-60% by weight; anddispersing the silicone aqueous emulsion release agent in water so as tohave a solids content of 2.5-30% by weight, wherein the vinyl-modifiedcollodial silica is obtained by reacting a colloidal silica with avinylalkoxysilane selected from the group consisting ofvinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane,allyltriethoxysilane, 3-(trimethoxysilyl)propyl acrylate,3-(trimethoxysilyl)propyl methacrylate, 3-(triethoxysilyl)propylacrylate, 3-(triethoxysilyl)propyl methacrylate,N-[3-(trimethoxsilyl)propyl]-N′-(4-vinylbenzyl)ethylenediaminehydrochloride.2. A method of preparing a silicone aqueous emulsion release liquidcomprising: preparing a silicone aqueous emulsion release agent having1-100% by weight of a dispersion of a vinyl-modified colloidal silicawith a solids content of 10-40% by weight, 0.1-5% by weight of adispersion of a platinum chelate catalyst with a solids content of12-25% by weight, and a remaining amount of the silicone aqueousemulsion release agent being of a polysiloxane water-dispersiblesilicone emulsion with a solids content of 30-60% by weight; anddispersing the silicone aqueous emulsion release agent in water so as tohave a solids content of 25-30% by weight, wherein the vinyl-modifiedcolloidal silica is obtained by reacting a colloidal silica with analkoxysilane having an amino group selected from the group consisting ofγ-aminopropyltrimethoxysilane, γ-aminoproyltriethoxysilane,γ-aminopropylmethyldimethoxysilane, γ-aminopropyldimethylethoxysilane,N-phenyl-γ-aminopropyltrimethoxysilane,N-phenyl-γ-aminopropylthriethoxysilane,N-β-(aminoethyl)-γ-aminoproplytrimethoxysilane,(aminoethyl)-γ-aminopropyltriethoxysilane,N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane,N-β-(aminoethyl)-γ-aminopropyldimethylethoxysilane,N′-[3-(trimethoxysilyl)propylldiethylenetriamine,N′-[4-(trimethoxysilyl)butyl]ethylenediamine and mixtures thereof,followed by further reacting with a carboxyl compound having a vinylgroup selected from the group consisting of acrylic acid, methacrylicacid, itaconic acid, vinylacetic acid, vinylpropionic acid and mixturesthereof.
 3. The method of claim 1, said platinum chelate catalyst beingselected from the group consisting of carbon-supported platinum,silica-supported platinum, chloroplatinate, platinum-olefin complexes,platinum-alcohol complexes, platinum-amine complexes and platinumcoordination compounds, said platinum chelate catalyst beingwater-dispersible.
 4. The method of claim 2, said platinum chelatecatalyst being selected from the group consisting of carbon-supportedplatinum, silica-supported platinum, chloroplatinate, platinum-olefincomplexes, platinum-alcohol complexes, platinum-amine complexes andplatinum coordination compounds, said platinum chelate catalyst beingwater-dispersible.
 5. A release film comprising: a polyester film; and asilicone aqueous emulsion release liquid applied on said polyester filmas a release layer, said silicone aqueous emulsion release liquidcomprising: a silicone aqueous emulsion release agent having 1-10% byweight of a dispersion of a vinyl-modified colloidal silica with asolids content of 10-40% by weight, 0.1-5% by weight of a dispersion ofa platinum chelate catalyst with a solids content of 12-25% by eight,and a remaining amount being of a polysiloxane water-dispersiblesilicone emulsion with a solids contend of 2.5-30% weight, said siliconeaqueous emulsion release agent dispersed in water so as to have a solidscontent of 2.5-30% by weight, said vinyl-modified colloidal silica isobtqained by reacting a colloidal silica with a vinylalkoxysilaneselected form the group consisting of vinyltrimethoxysilane,vinyltriethoxysilane, allythrimethoxysilane, allyltrimethoxysilane,3-(trimethoxysilyl)propyl acrylate, 3-trimethoxysilyl)propylmethacrylate, 3-(triethoxysilyl)propyl acrylate,3-(triethoxysilyl)propyl methacrylate,N-[3-(trimethoxysilyl)propyl]-N′-(4-vinylbenzyl)ethylenediaminehydrochloride.
 6. A release film comprising:a polyester film; and a silicone aqueous emulsion release liquid appliedto said polyester film as a release layer, said silicone aqueousemulsion release liquid comprising: a silicone aqueous emulsion releaseagent having 1-10% by weight of a dispersion of a vinyl-modifiedcolloidal silica with a solids content of 10-40% by weight, 0.1-5% byweight of a dispersion of a platinum chelate catalyst with a solidscontent of 12-25% by weight, and a remaining amount of the siliconeaqueous emulsion release agent being of a polysiloxane water-dispersiblesilicone emul sion with a solids content of 30-60% by weight, saidsilicone aqueous emulsion release agent in water so as to have a solidscontent of 25-30% by weight, said vinyl-modified colloidal silica beingobtained by reacting a colloidal silica with an alkoxysilane having anamino group selected from the group consisting ofγ-aminopropyldimethylethoxysilane, γ-aminoproyltriethoxysilane,γ-aminopropylmethyldimethoxysilane, γ-aminopropyldimethylethoxyilane,N-phenyl-γ-aminopropylthriethoxysilane,N-phenyl-γ-aminopropylthriethoxysilane,N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane,N-β-(aminoethyl)-γ-aminopropyltriethoxysilane,N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane,N-β-(aminoethyl)-γ-aminopropyldimethylethoxysilane,N′-[3-(trimethoxysilyl)propyldiethylenetriamineN′-[4-(trimethoxysilyl)butyl]ethylenediamine and mixtures thereof,followed by further reacting with a carboxyl compound having a vinylgroup selected from the group consisting of acrylic acid, methacrylicacid, itaconic acid, vinylacetic acid, vinylpropionic acid and mixturesthereof.